1. Field of the Invention
This invention relates to a new functionalized polypropylene composition and a new and improved process for the functionalization of polypropylene, particularly the maleation of polypropylene.
2. Brief Description of the Prior Art
To prepare polypropylene for certain end-use applications it is necessary to functionalize the polymer, i.e., to incorporate functional groups such as maleic anhydride onto the polypropylene polymer chains. The reaction of maleic anhydride with polypropylene is well known in the art. Examples of the prior art are U.S. Pat. Nos. 4,404,312; 4,506,056; 3,414,551; 4,370,450; and 4,639,495. European Patent application 0 225 186 is another example of a method of grafting maleic anhydride onto polypropylene. In the prior art, the maleation of polypropylene has been accomplished by the use of free radical initiators such as a peroxide initiator to induce maleation. However, the prior art peroxides which have been used for functionalizing polypropylene cause substantial degradation of the molecular weight of the maleated polypropylene. In an attempt to avoid molecular weight degradation of the maleated polypropylene the prior art methods employed low levels of peroxide initiator. See, for example, U.S. Pat. No. 4,404,312 which states that the organic peroxide should not be more than about 0.1 percent by weight, and preferably not more than 0.01 percent by weight of the polypropylene to be reacted. As a result, in the prior art, the extent of maleation of the polypropylene has been restricted. Other attempts to avoid the molecular weight degradation require the use of a third ingredient, such as styrene, which becomes a part of the polymer, or require the use of a catalyst such as N,N-dialkylethanolamine, or other nitrogen, phosphorus, or sulfur containing compounds. Examples of such ingredients are found in U.S. Pat. No. 4,506,056 and EPO Application 0 225 186.